Japan’s Supreme Court on Friday threw out two claims involving compensation for Chinese nationals forced to serve as labourers and prostitutes during the second world war, just as Shinzo Abe, the prime minister, wrestled with the issue of wartime sex slaves during his visit to Washington.

In the first case, the court overturned a landmark 2004 ruling by the Hiroshima high court that ordered Nishimatsu Construction to pay Y27.5m ($231,000, €169,000, £115,000) to two former labourers and the relatives of three deceased workers who claimed they were forced to work in severe conditions at a hydroelectric power plant construction site in Hiroshima prefecture during the war. The high court ruling had marked the biggest victory among a wave of compensation claims – most of which have been dismissed – filed in Japan since 1995 by Chinese nationals.

But Ryoji Nakagawa, presiding justice, said that under the 1972 Japan-China joint communiqué, Chinese individuals lost their right to claim war compensation from Japan, the Japanese people or companies. Under the communiqué, Beijing renounced any right to claim war reparations from Japan.

The plaintiffs claimed that the communiqué did not cover individual claims.

Justice Nakagawa added, however, that the victims of wartime forced labour had suffered “extremely large mental and physical suffering” and called on those ­concerned to “make efforts to provide relief to the ­victims”.

In the second case, the Supreme Court upheld a high court decision that the right of two Chinese women to claim compensation for forced wartime prostitution had lapsed.

The Supreme Court said that the right lapsed under the 1952 peace treaty between Japan and the Nationalist government, which had then fled to ­Taiwan but which Japan ­recognised as the legitimate government of China at the time.

The rulings come as the US Congress debates a resolution on seeking an apology from Japan for forcing young women to work in military brothels during the war.

Mr Abe, who last month ignited ­controversy with his remarks on the forced prostitution issue, expressed regret on Friday over the fate of the women in remarks to congressional leaders.

“I, as an individual and as prime minister, sympathise with the former ‘comfort women’ for their sufferings and feel sorry for the hardships they were put through,” he was quoted as saying in a meeting with 11 US lawmakers.